Horizontal Pulley Question [Forces]

[harujina]

Homework Statement

An object is hanging by a [mass-less] string on a [mass-less] pulley from a cart on a desk with a mass of 1.8 kg. The cart has an acceleration of 2.5 m/s^2. Calculate the mass of the hanging object given that:

a) There is no friction.
b) There is a frictional force of 0.4 N on the wheels of the cart.

Homework Equations

Fnet = ma

The Attempt at a Solution

m1 = 1.8 kg
a = 2.5 m/s^2
m2 = ?

I don't know where to start with this question...
Maybe Fnet = (1.8 kg)(2.5 m/s^2) = 4.5 N ? But what would I do with this.
... I don't know.

 

[Bryson]

What do you think the acceleration of the falling object is?

 

[harujina]

Isn't it the same?

 

[Bryson]

Perhaps, think about a force diagram. You have one force going downward and one upward. Draw it out, then solve for your unknown.